Tea bags of black tea, green tea, herb tea and the like, as well as extraction bags of soup such as dried sardine and dried bonito are made from a water filter sheet such as a nonwoven fabric and the like. The water filter sheet is formed into bag bodies in the shape of flat bags, tetrahedrons, or the like, each of the bag bodies is filled with extraction materials such as tea leaves and a hanging thread with a tag is bonded to the outer surface of the bag body so as to be used as the bags.
An extraction bag sheet for use in manufacturing such extraction bags is formed from a belt-like water filter sheet, on which a hanging thread with a tag for one extraction bag is repeatedly arranged in a longitudinal direction of the sheet at prescribed intervals. As an extraction bag sheet manufacturing apparatus which manufactures extraction bag sheets with high productivity, there is known an apparatus which arranges tags at prescribed intervals on a belt-like water filter sheet in the longitudinal direction of the sheet and arranges a long thread material so as to be placed over each of the tags (Patent Literatures 1 and 2).
The extraction bag sheet manufacturing apparatus manufactures extraction bag sheets by holding tags on a peripheral face of a rotary carrier at prescribed intervals, forming a long thread material into a continuous winding pattern on the rotary carrier so that the thread material is placed over those tags, welding the tags and the thread material together on the rotary carrier, then feeding a water filter sheet onto the rotary carrier, and welding the tags or the thread material to the water filter sheet.
The extraction bag sheet is applied to a packing machine, where both side-edge portions of the sheet are sealed (vertical sealing) together in the longitudinal direction to form a cylindrical body, and welding/melt-cutting (horizontal sealing) of the cylindrical body in a width direction and filling of contents are alternately repeated to manufacture extraction bags. In this case, if horizontal sealing is repeated in the same direction, flat bag-type extraction bags are obtained, whereas if the sealing is performed with the direction of the cylindrical body being repeatedly changed by 90 degrees on the plane vertical to the longitudinal direction of the cylindrical body, then tetrahedral extraction bags are obtained.
The thus manufactured extraction bags of both the flat-bag type and the tetrahedral type are configured so that the thread material and the water filter sheet are welded together on the upper and lower transverse seal portions of the extraction bags. Accordingly, in order to prepare an extraction bag to be used with the bag body of the extraction bag being hung with a hanging thread, it is necessary to strip the thread material from a transverse seal portion near the tag.
Meanwhile, with a recent increase in environmental consciousness, water filter sheets and/or thread materials made of biodegradation plastic have come to be used for extraction bags.
However, when extraction bags are manufactured from a water filter sheet and/or a thread material made from biodegradable plastic as described in the foregoing, the water filter sheet and the thread material are firmly welded. This causes the problem in that the water filter sheet is torn when the thread material is stripped from the transverse seal portion at the time where the extraction bag is used.
As a solution to such a problem, the thread material in the extraction bag sheet may be removed in advance from a horizontal seal formation portion where the thread material needs to be taken off at the time when the extraction bag is used. As a method for removing the thread material in a production line of the extraction bags, there is known a method in which cutting the thread material with use of a cutter, lifting the thread material, and cutting the thread material are performed in sequence (Patent Literature 3). This method may also be applied to manufacturing of extraction bag sheets.